Fitting for pipes and relevant pipe connecting method

ABSTRACT

A fitting for a pipe is disclosed. It includes a main body for internally accommodating the pipe, fastening means able to be tightened to the main body, a deformable annular sealing gasket and a blocking ring nut which can be positioned within the fitting between the main body and the fastening means, respectively, to ensure the sealing of, and block in firm position, the pipe, at least when the fastening means are tightened to the main body, the blocking ring nut being elastically deformable in radial direction. The fitting also has means for retaining in a widened position at least the mouth section of the annular sealing gasket, with an inner diameter greater than the outer diameter of the pipe.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.14/008,128, filed Oct. 23, 2013, which in turn is a 371 ofPCT/IB2012/000597, filed Mar. 26, 2012, which claims the benefit ofItalian Patent Application No. MI2011A000603, filed Apr. 11, 2011 thecontents of each of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention refers to a fitting for pipes and to a method forrelevant connection between at least one pipe and the above saidfitting.

BACKGROUND OF THE INVENTION

Fittings for pipes are known, made of plastic or metal, comprising amain body, also being made of plastic or metal, which internallyaccommodates an outer pipe, in order to connect it to a fluidic circuitplaced upstream or downstream of the fitting, and fastening means, alsomade of metal or plastic, able to be tightened to the main body.

Generally, these fastening means comprise a nut that can be screwed on acorresponding threaded region of the main body or, alternatively, a nut,or bush, constrained to the main body by tie rods, consisting of screwsor connecting bolts, for example.

Further, the main body accommodates an annular sealing gasket, oftruncated cone, cylindrical or toroidal shape, preferably made of rubberor deformable synthetic material, and a notched, or anyhow deformable,blocking ring nut (also termed “ogive”), also being truncated cone,cylindrical or toroidal, able to ensure, once the nut is tightened tothe main body, both the sealing, and the blocking of the pipe to thefitting in stable position, respectively.

According to the prior art there exist fittings of the above mentionedtype, wherein advantageously the annular sealing gasket and the blockingring nut are realized in a single piece.

In all of the above fittings, the outer pipe blockage within the fittingbody and the fluidic sealing of the fitting itself are usually ensuredby the interference coupling of conical walls, usually those of theinner surface of the fitting body and/or the relevant fastening nut withthe outer walls of the blocking ring nut and/or in case of the annulargasket, such that the tightening of the nut to the main body of thefitting determines the progressive engagement of the blocking ring nut,and possibly the gasket, with the inner walls of the fitting, whichwalls, due to different taper, cause the substantially radial crushingof such a blocking ring nut (ogive), and possibly the annular gasket, onthe outer pipe placed within the fitting itself.

This type of fitting, although rather efficient, has the drawback of notbeing easily connectable to the outer pipe, not allowing in fact theinsertion of the pipe within the fitting, when the nut is combined, oreven only partially screwed to the main body. In substance, beforeintroducing the pipe within the main body of the fitting the fasteningnut, the blocking ring nut (ogive) and the annular sealing gasket mustbe fitted (suited) onto the pipe and then, subsequently, when the pipeis completely introduced within the main body of the fitting, progressto first combining, and then tightening, the nut to the same main body.

This is mainly due to the fact that the annular sealing gasket,truncated cone or of other shape, if fitted within the main body beforethe pipe insertion, would be subjected, during the pipe insertion to ahardly amendable deformation, with subsequent sensitive reduction of thesealing efficiency of the fitting. The shape of the blocking ogives,with inner diameter substantially like outer diameter of the pipe andusually not elastically deformable, especially in radial direction, alsohelps avoiding that the pipe can be put into the fitting, or possiblywithdrawn, after this last one has been almost totally pre-assembled.

This problem is due to the strong friction and/or interference generatedbetween the inner surface of the annular sealing gasket, made of rubberor synthetic material, and the outer surface of the pipe, made of metalor plastic, during the insertion of the pipe within the fitting, andalso to the presence of a blocking ogive which, during the pipeinsertion, urges the annular sealing gasket to deform or results of hardsuitability or yet axially moves, hampering the possible pipe insertion.

Therefore these drawbacks are responsible of a highly complicated, slowand not always effective connection between pipe and fitting.

U.S. Pat. No. 3,140,107, for example, illustrates such a fitting that,even provided with an abutment ring interposed between the sealinggasket and blocking ogive, provides, mainly due to the shape andproperties of said blocking ogive, adopting the ring form with truncatedcone development, that the pipe is preventively fitted into thetightening nut, and thus into said ogive and sealing gasket, withrelevant abutment ring, before assembling the entire fitting.

The object of the present invention is, therefore, achieving a fittingable to make faster and, anyhow, reliable, the connection between thefitting itself and an outer pipe, avoiding the above mentioned technicaldrawbacks.

Further object of the present invention is achieving a connection methodbetween outer pipe and fitting which is simple, fast and effective.

SUMMARY OF THE INVENTION

These and other objects are achieved by the present fitting for at leastone pipe, comprising a main body for internally accommodating such apipe, fastening means which can be tightened to the main body, andwherein the main body internally accommodates at least a generallydeformable annular sealing gasket, provided with at least an mouthsection for the pipe, and at least a blocking ring nut (ogive) forfirmly and sealingly locking such pipe within the fitting, at least whensaid fastening means are tightened to the main body, and wherein suchblocking ring nut is elastically deformable at least in radialdirection. The fitting of the present invention also comprises,advantageously, means for retaining in a widened condition at least themouth section of the afore said annular sealing gasket with innerdiameter larger than the outer diameter of the external pipe.

Thus, due to the characteristic shape and properties of the blockingring nut and to the presence of these retaining means, the annularsealing gasket, preferably truncated cone and made of rubber or otherdeformable material, at least at its mouth portion, does not modify itsshape during the insertion of the pipe within the main body, therebymaking the insertion of the pipe itself within the fitting and itspossible withdrawal easy.

Next, once the pipe, made of a material selected from plastic, metal orplastic-metal composite, is inserted within the fitting, the sameannular sealing gasket and the same blocking ring nut, due for exampleto the above mentioned interference of conical surfaces, are suitablycompressed between the fastening means and the inside of the main body,such as to be able to respectively perform to ensure the seal of thepipe and retaining the pipe blocked within the fitting once thesefastening means, preferably consisting of a nut, are tightened to themain body of the fitting.

According to a preferred embodiment of the present invention, the aforesaid retaining means for example comprise stiffening means of the mouthsection of the annular sealing gasket and preferably comprising, forexample, at least an annular stiff element having an inner diameterlarger than the outer diameter of the pipe. This way, the pipe, at leastat the mouth portion of the annular sealing gasket, does notsubstantially comes into contact with a mild rubbing, or interference,that, anyway, is such that it does not cause any deformation of theannular sealing gasket itself during the insertion of the pipe withinthe fitting.

The annular stiff element, made of a material selected from plastic andmetal, can be removably combined within the seal gasket.

Such annular stiff element, for example, can be interference constrainedto the seal gasket, realizing the annular stiff element with its ownouter diameter slightly larger than the inner diameter of the mouthsection of the sealing gasket, so as to interfere with the latter,causing its widening at such mouth section. The sealing gasketelasticity, then, causes the annular stiff element to be constrained tosuch a gasket.

Alternatively, the annular stiff element can also be not removably, andthus irremovably, constrained to the sealing gasket. Such annular stiffelement, for example, once placed in interference with the sealinggasket, is glued and/or welded to the same gasket, or it can be moldedatop by the material forming the gasket.

According to a second embodiment of the invention, the annular stiffelement comprises at least an upper edge radially jutting with respectto its outer surface, to space the sealing gasket and the blocking ringnut between each other. Such annular stiff element takes a L-shapedprofile.

The spacing edge of the annular stiff element, during the tightening ofthe fastening means (a nut for example), lays between the sealing gasketand the blocking ring nut ensuring that, for extremely high tighteningmomenta, the sealing gasket holds its shape and functionality within thefitting.

Further, the presence of the jutting edge of the annular stiff elementplays the important role of avoiding that the blocking ring nut pinches,or damages, the gasket during the tightening of the nut, thus causing areduced efficiency of the gasket itself. At last, according to a furtherembodiment of invention, the blocking ring nut is provided with anending portion adapted to engage with the fastening means, consistingfor example in an appropriate nut. Specifically such a portion of theblocking ring nut end is concave such that it can accommodate an endingportion of the same fastening means.

The objects of the invention are also achieved by virtue of a method forconnecting a pipe to a fitting according to one or more of the claimsfrom 2 to 14, characterized by the fact of comprising the steps of: a)positioning said at least one annular sealing gasket and said at leastone blocking ring nut between the main body and fastening means; b)combining the fastening means (preferably made of an appropriate nut) tothe main body; c) inserting said at least one pipe within the fitting;d) tightening the fastening means to the main body. The method of thepresent invention is characterized by the fact that the afore said stepa) is anticipated by the step of retaining in widened position, by theafore said retaining means, with inner diameter larger than outerdiameter of the pipe, at least the mouth section of the annular sealinggasket.

Such solution allows, therefore, inserting/withdrawing the pipe withinthe fitting even when the nut is combined, or even only partly screwed,to the main body, since the pipe does not deform the sealing gasketduring the insertion into the fitting. The gasket remains stiff, atleast in its mouth section, due to the presence of said retaining meansplaced at the mouth section of the sealing gasket itself.

BRIEF DESCRIPTION OF THE DRAWINGS

A number of particular embodiments of the present invention will be nowdescribed, by way of example only and not of limitation, referring tothe attached figures, wherein:

FIG. 1a is a sectional view of an annular sealing gasket and acorresponding annular stiff element according to a first embodiment ofthe invention;

FIG. 1b is a sectional view of a fitting according to the firstembodiment of the invention represented in FIG. 1 a;

FIG. 2a is a sectional view of an annular sealing gasket and acorresponding annular stiff element according to a second embodiment ofthe invention;

FIG. 2b is a sectional view of a fitting according to the secondembodiment represented in FIG. 2 a;

FIG. 3 is a sectional view of a fitting according to a third embodimentof the invention;

FIG. 4 is a side sectional view of a fitting according to a furtherembodiment of the invention;

FIG. 5 is a perspective view of a blocking ring nut (ogive), accordingto a preferred aspect of the present invention; and

FIG. 6 is a perspective view of an annular stiff element, acting asmeans for retaining in widened position the mouth section of an annularsealing gasket of a fitting according to a particular embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring particularly to these figures a fitting according to theinvention has been indicated by the numeral 1. In FIGS. 1a and 1b afitting 1 according to a first embodiment of the invention isrepresented.

Such fitting 1 for a pipe 2, preferably made of polyethylene, comprisesa main body 3, with substantially cylindrical geometry and made ofmetal, able to internally accommodate the pipe 2, and fastening means 4that can be tightened to the main body 3. These fastening means 4, inparticular, comprise a nut, also made of metal that can be screwed to anappropriate threaded end 3 a of the main body 3.

It has to be observed that these fastening means 4 and the main body 3can also be made of plastic, or other material, without therebydeparting from the scope of protection of the present invention, as wellas can alternatively be made of a nut (or bush) constrained to the mainbody 3 by appropriate tie rods.

It has to be observed also that, whereas the embodiment of the fitting 1herein described is employed on plastic pipes, nevertheless fittings forthe employment with pipes made of metal material, or plastic-metalcomposite material, still fall in the protection scope of the presentinvention, as well as fittings for general flexible and/or deformablepipes.

The fitting 1 further comprises an annular sealing gasket 20, preferablyof truncated cone shape and made of rubber, or other (synthetic ornatural) deformable material, and a blocking ring nut 5, substantiallycylindrical in shape and made of plastic or metal. Such a blocking ringnut 5 is also termed “ogive” in the field.

Both the annular gasket 20, and the blocking ring nut 5 are shaped andplaced within the main body 3 and the relevant nut 4, such that the pipe2 can pass through them, or put into them, when it is inserted withinthe fitting 1.

In this regard, both the sealing gasket 20 and the blocking ring nut 5,are internally accommodated in the main body 3 of the fitting 1 at innerregions of the latter that allow, when the nut 4 is tightened on themain body 3, the firmly and sealingly coupling of such gasket 20 andblocking ring nut 5 on the pipe 2. Then, the gasket 20, and the ring nut5, both substantially annular, have thus a mouth section and an outletsection for the pipe 2.

In more detail, in the embodiment of the fitting 1 here shown andspecifically referring to FIG. 5, the blocking ring nut 5 is made by asubstantially cylindrical and/or truncated cone body, preferably made ofplastic or metallic material, which is provided with at least an axialnotch 21, not necessarily extended along the whole side surface of thering nut 5, that allows it, sometimes also in combination with theelasticity of the material composing such ring nut 5, to be at leastradially, and sometimes axially also, deformed (closed or open), andhaving some circular sealing ribs 22 on its inner surface. Such ablocking ring nut 5 is also designated to being accommodated, at leastpartially, within a region of the nut 4, having an inner truncated conesurface, having smaller diameter than that of the ring nut 5, when thelatter has its own notch open, in case upon its coupling with a pipe 2.

In other words, the blocking ring nut 5, or ogive can have a notchextended along the whole extension of its side surface, and thus have a“C” shaped cross section, susceptible to radial deformation by notchclosing/opening, or have, as in the here shown embodiment, one or morenotches 21 that, extended from one end to an annular portion 23 formingthe other end of the ogive 5, define two or more axially extended teeth,that can be radially moved closer/farther to each other for allowing theblocking of the pipe.

It has to be observed that such particular arrangement of the ogive 5gives substantial elasticity to the ogive itself, even when the materialforming the ogive 5 itself does not have excellent elastic properties,allowing it to elastically deform at least in radial direction.

As already described, in alternative embodiments not shown here, thering nut 5 can be free from radial notches and anyway have shape andphysical properties that allow it of being elastically deformed at leastin radial direction so that the pipe 2 fitted within it can be blocked,when tightening the nut 4 on the body 3 of the fitting 1, and as toallow to easily withdraw the pipe 2 itself, when the nut 4 is partiallyuntightened from the body 3.

Also observe that the blocking ring nut 5 can be made with such sizesand shape that, in unstressed condition, it shows an inner diameterlarger than the outer diameter of the pipe 2, or it can be made with ainner diameter smaller than the outer diameter of the pipe 2, but withthe ability of being radially extended (due for example to the aforesaid notch) when inserting the pipe 2 itself.

As known in the art, referring back to the particular embodiment of thering nut 5 shown here, before the tightening of the nut 4 on the mainbody 3, the blocking ring nut 5 is contained within the fitting 1 withits notch open, in case due to the insertion within it of the pipe 2,that is shaped in such a way that it has maximum diameter, while whenthe nut 4 is tightened on the main body 3, such a ring nut 5 is urged,by the interference with the gasket 20, or with possible frames insidethe main body 3 of the fitting 1, within the region with truncated coneinner surface of the nut 4, so as to narrow itself, by closing the notchand taking a shape with minimum diameter for internally blocking thepipe 2.

Substantially, when the nut 4 is completely tightened to the main body3, the blocking ring nut 5 is moved from its starting position towards aconical region that, interfering with such a ring nut 5, determines itssmooth crushing on the pipe 2. Advantageously, according to the presentinvention, the fitting 1 comprises means 7 for retaining in widenedposition the mouth section 20 a of the annular sealing gasket 20 suchthat the inner diameter of such mouth section 20 a is larger than theexternal diameter (De) of the pipe 2, so as to make the entry of thepipe 2 itself within the fitting 1 easy.

According to a preferred aspect of the present invention, theseretaining means 7 comprise means able to stiffen the mouth portion 20 aof the annular sealing gasket 20, so as to ensure that the externaldiameter (De) of the pipe 2 is always smaller than the inner diameter ofthe mouth section 20 a of the gasket 20 and thus ensure the easy slidingof the pipe 2 within such a mouth section 20 a, and thus within thesealing gasket 20.

This way, due to the presence of such retaining means 7, the annularsealing gasket 20, at least at its mouth section 20 a, does not comessubstantially into contact by friction, or interference, with the pipe 2during the insertion of the latter within the main body 3, thus makingthe insertion within the fitting 1 easy, even when the latter is atleast partially mounted.

That is, as long as the blocking ring nut 5 is not urged in its minimumdiameter position within the nut 4, that is as long as the latter hasnot being closingly tightened on the main body 3, the pipe 2 can beinserted within the fitting 1, the latter being assembled, but with thenut 4 only partially screwed, without this causing a harmfulinterference of the inlet end of the pipe 2 on the sealing gasket 20.

In effect, when the pipe 2 enters within the fitting 1, through theinlet section of the nut 4, the relevant inlet end in the fitting 1meets the blocking ring nut 5 first, in its arrangement with maximumdiameter larger than the outer diameter of the pipe 2, or in analternative arrangement thereof with diameter able to be widened due tothe insertion of the pipe 2 itself, and then the mouth section 20 a,suitably stiffened, or at least retained in a widened condition, by thegasket 20, which has a inner diameter larger than the outer diameter Deof the pipe 2, so as to favor the sliding of the pipe 2 within the wholesealing gasket 20, without causing interferences between the latter andthe pipe 2 itself, and instead allowing the perfect insertion of thelatter within the gasket 20.

Next, once the pipe 2 is inserted within the fitting 1, the sealinggasket 20 and the blocking ring nut 5 itself are suitably compressedbetween the nut 4 and the inside of the main body 3, such as to be ableto serve to respectively ensure the seal of the pipe 2 and retain thepipe 2 blocked within the fitting 1, once the fastening means 4 (nut)are tightened to the main body 3 of the fitting 1.

According to a further aspect of the present invention, the retainingmeans 7 can preferably comprise an annular stiff element having an innerdiameter Di larger than the outer diameter De of the pipe 2, on whichthe annular sealing gasket 20 is externally put on, at its mouth section20 a. This way, the pipe 2, at least at the mouth portion 20 a of thesealing gasket 20, never enters into contact with the gasket 20 itselfand thus the latter is prevented from crushing on itself during the pipe2 insertion within the fitting 1 and the tightening of the fasteningmeans (nut) 4 to the main body 3.

Such annular stiff element 7, made of a material selected from plasticand metal, but specifically metal (brass for example), can be removablyinterference combined within the annular sealing gasket 20. Practically,the outer diameter of this annular stiff element 7, which is larger thanthe inner diameter of the mouth section 20 a of the sealing gasket 20,interferes with the latter causing at least the widening of the mouthsection 20 a of the sealing gasket, made of deformable material. Theelasticity of the sealing gasket 20, then, causes the annular element 7to remain constrained to the gasket 20 itself.

According to a particular embodiment of the invention herein not shown,the annular stiff element 7 can be irremovably, thus firmly constrained,to the sealing gasket 20. For example, such annular element 7, onceplaced in interference with the sealing gasket 20, can be glued and/orwelded to the annular sealing gasket 20 itself such that it can be nomore unconstrained from the latter, or it can be substantially realizedin a single piece with the sealing gasket 20, for example by moldingatop the material forming the gasket 20 on the annular stiff element(preferably made of metal).

According to a second embodiment of the invention (FIGS. 2a and 2b ),the annular element 7 comprises a radially jutting edge 7 b with respectto its outer surface 7 a, to substantially space the sealing gasket 20from the blocking ring nut 5. Such annular stiff element 7 takestherefore a “L”-shaped profile.

This “L”-shaped profile, therefore, not only makes the insertion of theannular element 7 within the sealing ring easy, by widening it, but alsoallows to aid a homogeneous distribution of the thrust strength exertedby the blocking ring nut 5 on the sealing gasket 20, when the fasteningmeans (nut) 4 are tightened to the main body 3.

In fact, during the tightening of the fastening means 4, the juttingedge 7 b remains arranged between the annular sealing gasket 20 and theblocking ring nut 5, thereby ensuring that, for high tightening momenta,the sealing gasket 20 yet preserves its shape and functionality withinthe fitting 1.

Further, the presence of the jutting edge 7 b has the important functionof avoiding that the blocking ring nut 5 pinches, or damages, the gasket20, during the tightening of the nut 4, thus causing a reducedefficiency of the sealing gasket 20 itself. Moreover, such jutting edge7 b also provides a not deformable stop abutment for the gasket 20, whenthe annular stiff element 7 is combined to the latter.

As shown in FIG. 4 and FIG. 6, illustrating a further embodiment of thepresent invention and wherein like reference numbers for like parts inthe preceding figures have been used, alternatively, or in conjunctionto the above “L” shape, the annular element 7′ can also show a furtherradially jutting step 7′c, or other equivalent radially jutting couplingelement, that can be, for example, arranged in an ending portion of theannular element 7′ opposite with respect to that from which the edge 7 bprojects and which is intended to engage, by geometrical juxtaposition,with a relevant and complementary seat, or recess, internally obtainedwithin the sealing gasket 20, or can simply elastically deform the innerwall of the sealing gasket 20, substantially catching hold of it.

Such radially jutting element 7′c (step) of the annular element 7′serves to anchor such annular element 7′ to the sealing gasket 20, by—atleast—simple elastic deformation of the latter, by making the assemblingof the annular stiff element 7′ with the gasket 20 highly simplified.

In case the annular element 7′ results provided with both the juttingedge 7 b, intended to be arranged over the gasket 20 end, and thejutting frame 7′c, intended to engage within the relevant inner seat ofthe gasket 20 itself, such annular element takes therefore asubstantially “U”-shaped profile.

Finally, according to a further embodiment of the invention (see FIG.3), the blocking ring nut 5 can be provided with an ending portion 60able to be engaged with the fastening means 4, that is the nut 4, since,according to a particular aspect of this invention, the ending portion60 on the ring nut 5 is concave, such that it can accommodate acorresponding ending portion 80 of the nut 4.

As the skilled in the art could have appreciated from the abovedisclosure, the combination of the ring nut 5, with an inner diameterlarger than the outer diameter (De) of the pipe 2, or with an outerdiameter able to be widened when the pipe 2 engages it, and mainlyelastically deformable at least in radial direction, advantageously dueto the notches or notch provided on it, and to the above mentioned means7 or 7′ for retaining in widened position at least the mouth section 20a of the annular sealing gasket 20, allow the pre-assembling of thefitting 1 in all of its parts, including the fastening means (nut) 4,yet untightened, and only subsequently inserting the pipe 2 within thepre-assembled fitting 1, without this insertion in the pipe 2 beinghampered by undeserved deformations of the gasket 20 and/or by offsetsof the ring nut 5.

It has to be observed that the particular shape and elasticdeformability properties of the ring nut 5 and the presence of saidmeans 7 or 7′ for retaining in widened position at least the mouthsection 20 a of the annular sealing gasket 20, allow to easily withdrawthe pipe 2 from the fitting 1, when the fastening means (nut) 4 arepartially untightened.

Therefore, according to the invention, it is also provided a method forconnecting a pipe 2 to a fitting 1 of the above disclosed type. Such amethod comprises the steps of: a) positioning the annular sealing gasket20 and the blocking ring nut 5, at least radially deformable and with aninner diameter larger than outer diameter of the pipe 2, between themain body 3 and the fastening means (the nut 4 for example); b)combining the fastening means 4 to the main body 3, without tighteningthem; c) inserting the pipe 2 within the fitting 1 (through the mouthsection of the fastening means 4); and d) tightening the fastening means4 to the main body 3.

Advantageously the afore said step a) of the method is preceded by thestep of retaining in widened position, by means of suitable retainingmeans 7 or 7′, the mouth section 20 a of the annular sealing gasket 20such that the inner diameter results larger than the outer diameter ofthe pipe 2.

By doing so, it has to be observed that the steps a) and b) of the abovedisclosed method can be realized by only the manufacturer of the hereinclaimed fitting 1, while the next steps c) and d), that is the insertionof the pipe 2 and complete tightening of the fastening means 4, arereferred to the final user.

It has to be observed that, partially untightening the fastening means4, with the fitting 1 still mounted, the pipe 2 can be easily withdrawnfrom the fitting 1 itself, without the need of totally disassembling thelatter, due to the elastic deformability, at least in radial direction,of the ogive 5 and the stiffness of the end of the sealing gasket 20,given it by the retaining means 7 or 7′.

Such a repartition of the steps of the method for connecting a pipe 2 toa fitting 1 subject of this invention, shows to be particularlyefficient, since, differently from the known art, it makes the mountingof the fitting 1 by the final user unnecessary, also making theinsertion, but also withdrawal operations of the pipe 2 within thefitting 1 itself, easy.

As it is evident from the above provided disclosure of the fitting 1,such solution allows, therefore, to insert/disconnect the pipe 2 withinthe fitting 1 even when the nut 4 is combined or even only partiallyscrewed, to the main body 3, since it does not deform the annularsealing gasket 20 during its introduction/withdrawal in the fitting 1,nor provides a deformation of the ogive 5 preventing the ogive elasticcoming back to such an arrangement that allows the internally sliding ofthe pipe 2. The gasket 20 can thus remain substantially stiff due to thepresence of the afore said retaining means 7 or 7′, at least at themouth section 20 a of the sealing gasket 20 itself and the ogive 5 doesnot prevent the insertion/disconnection of the pipe 2.

The invention claimed is:
 1. A fitting for a pipe, comprising a mainbody for internally accommodating said pipe, a nut or bush able to betightened to said main body, said main body accommodating a deformableannular sealing gasket that is provided with a mouth section for saidpipe, and a blocking ring nut for firmly and sealingly locking said pipeat least when said nut or bush is tightened to said main body, saidblocking ring nut being elastically deformable at least in radialdirection, said blocking ring nut having circular sealing ribs on aninner surface thereof, said fitting comprising an annular stiff elementhaving an inner diameter (Di) larger than the outer diameter (De) ofsaid pipe, the annular stiff element interfering with the internalsurface of the mouth section of said annular sealing gasket causing thewidening of the mouth section of the annular sealing gasket, the annularstiff element being interposed between and being in contact with theannular sealing gasket and the blocking ring nut, and the circularsealing ribs of the blocking ring nut configured to contact the pipe. 2.The fitting according to the claim 1, wherein said annular stiff elementcomprises a coupling element, radially jutting, for the engagement withpart of the inner surface of said sealing gasket.
 3. The fittingaccording to claim 1, wherein said annular stiff element can beremovably combined to said gasket.
 4. The fitting according to claim 1,wherein said annular stiff element is immovably fastened to said gasket.5. The fitting according to claim 4, wherein said annular stiff elementis welded and/or glued to said sealing gasket, or said sealing gasket ismolded atop to said annular stiff element.
 6. The fitting according toclaim 1, wherein said main body has a tapered surface configured tocontact an external surface of the annular sealing gasket.
 7. Thefitting according to claim 1, wherein said annular stiff elementcomprises a radially jutting edge with respect to its outer surface tospace said sealing gasket and said blocking ring nut from each other, atleast when said a nut or bush are tightened to said main body.
 8. Thefitting according to claim 1, wherein said blocking ring nut comprisesan axial notch.
 9. The fitting according to claim 1, wherein saidsealing gasket is made of rubber or other synthetic or naturaldeformable material.
 10. The fitting according to claim 1, wherein saidannular stiff element is made of a material selected from plastic and/ormetal.
 11. The fitting according to claim 1, wherein said blocking ringnut is provided with an ending portion that could be engaged to said nutor bush.
 12. The fitting according to claim 11, wherein said endingportion is concave to accommodate a tapered ending portion of said nutor bush.
 13. The fitting according to claim 1, wherein said pipe is madeof a material selected from plastic, metal or a plastic-metal composite.14. The fitting according to claim 1, wherein said annular gasket has atruncated cone, or cylindrical or toroidal development.
 15. A fittingfor a pipe, the fitting comprising a main body for internallyaccommodating said pipe, a nut or bush able to be tightened to said mainbody, said main body accommodating a deformable annular sealing gasketthat is provided with a mouth section for said pipe, and a blocking ringnut for firmly and sealingly locking said pipe at least when said nut orbush is tightened to said main body, said blocking ring nut beingelastically deformable at least in radial direction, said blocking ringnut having circular sealing ribs on an inner surface thereof, thecircular sealing ribs of the blocking ring nut configured to contact thepipe, said fitting comprising an annular stiff element having an innerdiameter (Di) larger than the outer diameter (De) of said pipe, theannular stiff element interfering with the internal surface of the mouthsection of said annular sealing gasket causing the widening of the mouthsection of the annular sealing gasket, the annular stiff element beingprovided with a radially jutting coupling element for the engagement ofsaid annular stiff element to the annular sealing gasket by means ofelastic deformation of the annular sealing gasket.